The Australian Human Rights Commission says the policy under which asylum seekers are being held on Nauru is a breach of international law.

Tensions are escalating on the Pacific island with reports a large group of asylum seekers have joined a hunger strike and at least one has self-harmed in protest at their detention.

Australia's Department of Immigration confirmed that about 170 men are engaged in a "peaceful protest" and many are refusing food.

The president of the Australian Human Rights Commission, Professor Gillian Triggs, told ABC Radio Australia's Pacific Beat that she believes laws are being broken and is considering taking the case to the UN Human Rights Committee.

"Our position at the Australian Human Rights Commission is that this is an egregious breach of refugee law and of general international law," Prof Triggs said.

"It amounts to an arbitrary detention of asylum seekers and really is unacceptable."

Uncertainty prevails

One man who said he was taking part in the hunger strike told the ABC that the asylum seekers' mental health is suffering because of the indeterminate nature of their detention.

"Most of the people here now they cannot sleep, they cannot do any activity," he said.

"If you ask immigration they don't know anything. They don't answer your questions about how will be the processing, how will be the future. They don't answer."

The man claimed that he witnessed acts of self-harm daily, but Australia's Department of Immigration says they are not keeping records on the number of self-harm incidents.

Mental impact

Dr Graham Thom, the refugee coordinator with Amnesty International Australia, said he expected the protests would continue to intensify.

"It's the mental impact that's most difficult to mitigate against and that mental impact is exacerbated by uncertainty," Dr Thom said.

"When you hold vulnerable people in uncertain conditions, when they don't know when the process is even going to start, that's when you start to see problems."